(1) Field of the Invention
The present invention generally relates to acoustic transducers and more particularly, to slotted cylinder acoustic transducers.
(2) Description of the Prior Art
An acoustic transducer possesses the capability to transfer mechanical energy to electrical energy and vice versa. Typically, the acoustic transducer utilizes piezoelectric materials that react to pressure differentials by emitting an electrical charge. Therefore, any pressure wave impinging on an underwater transducer will generate an electrical charge proportional to the magnitude of the pressure. As a result, one can monitor underwater pressure differentials by monitoring the output charge from the piezoelectric material and associated transducer—in an operation very similar to the use of an underwater microphone.
Alternately, by controlling the input voltage magnitude and signal characteristics, one can generate equivalent pressure waves underwater with a result very similar to an underwater speaker. Examples of such tasks for underwater acoustic transducers include scanning for shipwrecks or other underwater objects; probing the ocean floor for oil reserves; and monitoring temperature fluctuations in the ocean.
Slotted cylindrical acoustic transducers, also known as Slotted Cylinder Projectors (“SCPs”), are known in the art. Many prior art slotted cylindrical acoustic transducers use piezoelectric material (i.e. lead zirconate titanate, or PZT) as an active material. In a typical slotted cylindrical acoustic transducer, piezoelectric plates are adhesively bonded to the inner wall of a slotted cylindrical shell. The slots runs along the length of the cylinder. A cylinder can have either a constant-wall thickness or a tapered-wall thickness.
Slotted cylinder acoustic transducers are described in U.S. Pat. Nos. 6,002,649, 6,678,213 and 7,719,926. U.S. Pat. No. 6,002,649, entitled “Tapered Cylinder Electro-Acoustic Transducer with Reversed Tapered Driver” describes an electro-acoustic transducer that uses a cylinder having a tapered thickness. A piezoelectric driver element is located in the interior cavity of a cylindrical shell. The shell is fabricated from a metal or a laminated composite material. The driver element is mechanically-connected to the cylindrical shell by an epoxy bond between the outer surface of the driver element and the inner surface of the cylindrical shall. The driver element comprises a plurality of piezoelectric ceramic elements circumferentially arranged in a stack.
U.S. Pat. No. 6,678,213, entitled “Slotted Cylinder Transducer with Trapezoidal Cross-Sectional Electrodes” describes a slotted cylinder transducer that uses a cylinder that has a uniform thickness. A plurality of ceramic elements and electrodes are alternately disposed circumferentially on the inner surface of the cylinder.
U.S. Pat. No. 7,719,926, entitled “Slotted Cylinder Acoustic Transducer”, describes a slotted cylinder acoustic transducer that has a slotted cylindrical shell and a stack of piezoelectric ceramic elements that are bonded to the inner wall of the cylindrical shell. Electrodes are interposed in the stack of piezoelectric ceramic elements, wherein one electrode is positioned between a pair of adjacent piezoelectric ceramic elements. The slotted cylindrical shell has a tapered thickness.
Other acoustic transducer devices that use conventional piezoelectric material are described in U.S. Pat. Nos. 2,812,452, 3,773,898, 4,220,887, 4,257,482, 4,651,044, 5,229,978, 6,069,845, 6,285,631 and 6,781,288. Ferroelectric crystals are described in U.S. Pat. No. 3,773,898, entitled “Compound Ferroelectric-Ferroelastic Crystal”, and in U.S. Pat. No. 5,998,910, entitled “Relaxor Ferroelectric Single Crystals For Ultrasound Transducers”.
What is therefore needed is an improved slotted cylinder acoustic transducer that is relatively smaller in size and lighter in weight than the aforesaid prior art slotted cylinder acoustic transducers but yet is capable of providing the same acoustic power output as prior art slotted cylinder acoustic transducers.